METEORIC AND ARTIFICIAL NICKEL-IRON ALLOYS. 
91 
the critical point was continuous. That such effects are to be expected will be seen 
on consideration of fig. 27, VI. If the cooling is interrupted at a comparatively high 
temperature such as v lf crystallisation will proceed from the metastable solution 
during subsequent reheating to w x and cooling to x v At the latter point the bulk 
of the solution has again reached the temperature of lability, and crystallisation 
proceeds by generation of fresh nuclei. But the solution from which crystals 
separated, during the treatment ViW x x y , has become relatively rich in nickel and will 
not become labile until a temperature lower than x 1 is reached. The value of this 
temperature will depend upon the amount of crystallisation that ensues during the 
process Viw x x x . 
If it is comparatively small, the whole of the solid solution remaining at may be 
in the labile state, and crystallisation during further cooling will take place in the 
same way as when the cooling from C is uninterrupted. 
If, however, there is a considerable amount of re-crystallisation during the process 
VxWiX ly or if the amount is increased by repetition of the process as in the case 
v 2 w 2 x 2 y 2 z 2 , then the solution from which crystals have been deposited round nuclei 
may have become so rich in nickel that it does not become labile until a low tempe¬ 
rature, such as p 2 , is attained. The mean permeability of the material at the air 
temperature may then be relatively low. 
Examples of the correspondence between these conclusions and the experimental 
data are given below. 
Meteoric Iron I. v (45), iv (46), x (47). 
Here the range of the alternation is about 60° C. and the permeability x is about 
8|- per cent, greater than the permeability v. 
The subsequent air temperature permeability (Experiment 48) is about 4 per cent, 
less than that obtained after continuous cooling (cf Experiment 49). 
Meteoric Iron II. (Curves, fig. 11). v (26), w (27), x (28). 
Here the range of the alternation is about 100° C. and the permeability x is about 
16 per cent, greater than the permeability v. 
The subsequent air temperature permeability (29) is about 6 per cent, less than 
that obtained after continuous cooling (ill). 
v (30), iv (31), x (32), y (33), 2 (34). 
Here, after two alternations over a range of about 100° C., the subsequent air 
temperature permeability (35) is about 11 per cent, less than after continuous cooling 
(Experiment 111). 
